The present invention relates to an image forming apparatus for image formation in accordance with input image data, and particularly to an image forming apparatus having a power-saving operation mode.
In image forming apparatuses such as a printer or a copying machine, attention has been focused on reducing standby power consumption to a minimum level. One known solution is to incorporate a power supply device that stops power supply from a main power supply circuit during standby time.
However, an image forming apparatus on standby is sometimes required to return to a normal operation mode in response to external input signals. During standby time, a copying machine with facsimile functions, for example, needs to be ready to appropriately receive facsimile data input externally over telephone lines. A printer needs to return to a normal operation mode immediately on detection of image data input from a personal computer and perform an image forming operation according to the input image data.
Japanese Patent Application Laid-Open No. 2001-94693 discloses an image forming apparatus capable of returning from a power-saving operation mode to a normal operation mode appropriately as necessary.
The image forming apparatus, however, switches between the two operation modes regardless of a state of power supply from a main power supply to different components of the apparatus. Accordingly, switching of the operation modes cannot be optimized according to the power supply conditions, thereby taking excessive time.
A feature of the present invention is to offer an image forming apparatus that is ready to receive external signals with minimum power consumption in a power-saving operation mode.
Another feature of the present invention is to offer an image forming apparatus capable of switching between operation modes in a short time.